FIELD OF THE INVENTION
This invention relates to an antifouling composition for preventing the adhesion of marine organisms, including marine microorganisms, to surfaces.
The adhesion of marine fouling animals such as Barnacles, Hydroides, Membraniporas, Bugulas, Mutilus, and Sponges and marine fouling plants such as Entermorphas, Ulva, Bangia, and the like which grow on the sufaces of ship's hulls at the bottom or water line part, on the inner surface of sea water uptake gates or cooling tubes of thermal or nuclear electric power plants, on the surface of apparatus or culture nets of sea-water culture installations and so on, gives adverse effects such as the reduction in ship velocity or in water-uptake capacity of the plants and the slowdown in growth of the cultured fishes.
In order to prevent these adverse effects, antifouling compositions which contain cuprous oxide, organo tin compounds, organo-tin polymer, thiocarbamates or the like have been hithertofore invented and used. These antifouling compositions are sufficiently effective with respect to the marine fouling organisms such as the above-stated marine fouling animals or plants, which grow to sizes from few to several hundred millimeters so that they can be observed by the naked eye, and therefore, they are actually and widely used.
However, marine microorganisms, of which grown individuals can hardly be seen by the naked eye, were recently found to contribute to the adhesion of the marine organisms, including the above-stated adhesive marine organisms.
Examples of the marine microorganisms are as follows: marine bacterial strains of Bacillus subtilis, of genera Achromobacter, Micrococcus, Pseudomonas, Caulobacter, Saprospira, Sarcina, Flavobacterium and the like; marine fungal strains of genera Aspergillus, Nigrospora, Penicillium and the like; and marine diatomaceous strains of genera Navicula, Melosira, Nitzschia, Licmophora, Biddulphia, Thalassionema, Achnanthes, Asteromphalus, Diatoma, Phabdonema, Synedra and the like.
The adhesion of the marine microorganisms causes an increase in the frictional resistance of the ships hull surface which results in excessive fuel consumption and additional running costs.
In the cooling systems of electric power plants, their heat exchangers are reduced in the heat exchange efficiency by the adhesion of the marine microorganisms.
In fish culture nets, many disturbances, such as delayed growth of the fishes due to the insufficiency of oxygen content in the sea water, are caused since inflows and outflows of sea water through the nets are restricted by the adhesion of the said marine organisms on the net cords.
The fouling damage caused by the adhesive marine organisms is initiated at the first stage by the adhesion of these marine microorganisms and then the adhesion of larvae of larger adhesive organisms occurs at the second stage. Therefore, prevention of the adhesion of the marine microorganisms is effective to prevent the adhesion of adhesive organisms thereafter and makes it possible to completely inhibit the fouling.
However, marine microorganisms such as marine bacteria, Marine fungi and Marine Diatoms inherently show considerably stronger resistance to various chemical substances as compared with larvae of Barnacles, Bugulas, Enteromorphas and the like, and conventional antifouling compositions can hardly prevent the adhesion of these marine microorganisms.